Vacuum cleaning is a well-known method for removing dust from surfaces, particularly floors. In general, in the field of vacuum cleaning, a suction force is generated and applied for forcing dust particles to move from a surface to be cleaned to another location such as a canister for collecting the particles. In the process, it may be desirable to agitate the surface in order to facilitate removal of the particles from the surface under the influence of the suction force as mentioned. To that end, it is possible to use a tool for actually contacting the surface to be cleaned. However, it is also known to use another technique, namely a technique which involves the use of a kind of air pump, wherein air waves are generated for vibrating the surface, which can help in releasing dust particles from the surface.
U.S. Pat. No. 7,383,607 discloses an agitation apparatus which is suitable for use in a cleaning head of a vacuum cleaner, and which includes first and second flow paths. Each of these flow paths has a resonant cavity and an inlet/outlet port which joins the cavity to a space within the cleaning head. A generator, such as a loudspeaker with a diaphragm, generates an alternating pressure wave between the ports. Pressure waves are emitted from one of the ports in an anti-phase relationship with the pressure waves from the other of the ports, thus reducing operating noise. When the vacuum cleaner of which the agitation apparatus is part is used for cleaning a carpet, the air motion to/from the ports vibrates the pile of the carpet and serves to draw out dust from between the carpet fibers.
It is noted that the agitation apparatus known from U.S. Pat. No. 7,383,607 helps in releasing dust from a carpet, but there is also a problem associated with this apparatus, which resides in the fact that both resonant cavities are in communication with a space within the cleaning head, through a port. As a result, among other things, it is possible for dust particles to reach the backside of the generator, which is present in one of the cavities. In this way, the functioning of the means for actuating the movable surface of the generator, which are arranged at the backside of the generator, may get disturbed, and it may eventually even be so that the accumulation of dust leads to total failure of the generator.